The present invention relates to spectrophotometers, and more particularly to spectrophotometers having selectable measurement areas.
Spectrophotometers are instruments used to determine the color of an object. A spectrophotometer typically includes a source of illumination to illuminate the object, a color measurement engine for detecting light reflected from the sample; and signal processing circuitry connected to the light measurement engine to compute curves or numerical values indicative of color. The general principles of construction and use of spectrophotometers are well known to those skilled in the art.
One type of spectrophotometer uses an integrating sphere in which the light illuminating the sample is integrated to provide diffuse, uniform illumination over an exposed measurement area of the sample. An example of such a spectrophotometer is illustrated in U.S. Pat. No. 5,369,481, issued Nov. 29, 1994 to Berg et al and entitled "Portable Spectrophotometer." This device provides a measurement area that is a circle of fixed diameter. Unfortunately, in order to sample measurement areas of different sizes, multiple devices designed for different measurement areas must be used. Alternatively, portions of the optics or the color measurement engine of a single device can be manually interchanged to accommodate different measurement areas, but this requires undesirably complicated user procedures.